Aperture Synthesis in Radar Astronomy and Some Applications to Lunar and Planetary Studies

The fading of a radar return from a planetary surface can be interpreted as a drift of a random diffraction pattern over the receiving antenna. Measurement of the signal autocorrelation function can, therefore, be interpreted as a spatial correlation (visibility) along the direction of drift. With two spaced antennas the cross‐correlation of the received signals with variable time shifts is shown to lead to a variable effective baseline. It therefore takes only a one‐dimensional array of receiving antennas to completely cover the two‐dimensional correlation plane. Aperture synthesis technique as discussed is applied to the mapping of the lunar surface at 23 cm.